This post from Jeremy only just now crossed my path, but I love it. My latest talk discusses how important it is to have a shared set of principles that help people understand what they should do (and not do) and why.
Those sound like good use cases to me. Those are situations when design principles can help people reach agreement on priorities, without it having to be about ego or who shouts loudest.
Emphasis mine here. Design principles can help neutralize a lot of the thorny political, personality-driven conflict that inevitably happens when working with other people.